Knowledge of the void fraction within the bed of a fluidized-bed combustor or gasifier is vital to the design and operation of such units. Predictive modeling of fluidized-bed performance is also highly dependent upon a broad data base of dynamic void fraction information for various bed geometries, size, and bed conditions.
A two-dimension and three-dimension density imaging system in wide spread utilization today is the computerized axial tomography system. The systems are typically used in medical and industrial applications. However, these nuclear-based scanning systems are very bulky, massive, and expensive. Furthermore, the systems scan at a slow rate due to the mechanical scan method employed and the nuclear event counting time required. Such a system would not be suitable to study dynamic fluidized-bed behavior, where rapid three-dimension mapping of a bed density field is required. In some applications, mapping rates of one hundred times per second will be necessary.